code: def _buySignal(self, price):
      buyOrders, sellOrders = self._getActiveOrders()
      self._cancelOrders(sellOrders)
  
      brk = self.getBroker()
      cashAvail = brk.getCash() * 0.98
      size = round(cashAvail / price, 3)
      if len(buyOrders) == 0 and price * size > VWAPMomentum.MIN_TRADE:
          self.info("Buy %s at %s" % (size, price))
          try:
              self.limitOrder(self.__instrument, price, size)
          except Exception as e:
              self.error("Failed to buy: %s" % (e))
  
file_path: pyalgotrade/samples/bccharts_example_2.py
imports: from pyalgotrade import bar
  from pyalgotrade import strategy
  from pyalgotrade import plotter
  from pyalgotrade.technical import vwap
  from pyalgotrade.barfeed import csvfeed
  from pyalgotrade.bitstamp import broker
  from pyalgotrade import broker
label_desc: Use image node_id 4 for calling the VWAPMomentum obj's underlying member method code with example usage: obj._buySignal(price) without return types